1. Field of the Invention
The invention relates to a valve device and, more particularly, to a weight-reduced valve device that is applicable to a gas tank that stores a high-pressure gas such as hydrogen gas or the like.
2. Description of the Related Art
The tap body that closes an opening portion of a gas tank that stores a high-pressure fluid is provided with a valve device which has one or more passages that connect between the inside and the outside of the gas tank, and which controls the flow of gas within the passages. An example of the valve device is a pressure reducing valve that controls the pressure of the gas that is led to the outside.
The valve device has a valve member that includes a valve element and the like, and also has a body within which a valve insertion hole in which the valve member is mounted is formed. An end of a lead-in passage that introduces the high-pressure fluid has an opening to the valve insertion hole.
By the way, vehicles that employ fuel cells are being developed in recent years. In a method of a fuel cell, high-pressure hydrogen gas is used as a fuel. The gas tank used to store the high-pressure hydrogen gas, including attachment appliances, such as the valve device and the like, is required to have a reduced weight. For example, in order to reduce the weight of the valve device, an attempt to form a body from an aluminum alloy whose specific weight is small is being made (Japanese Patent Application Publication No. 2005-325891 (JP-A-2005-325891), and the like).
Incidentally, since the valve member needs to have a certain degree of size, the inside diameter of the valve insertion hole in which the valve is mounted is larger than the inside diameter of the lead-in passage through which a high-pressure gas is introduced. Therefore, in the case where an end of the lead-in passage is opened to the interior of the valve insertion hole, the opening of the end of the lead-in passage is formed in the relatively smooth inner surface of the valve insertion hole. Therefore, a sharp angle is formed at the opening portion where the lead-in passage is opened to the inner surface of the valve insertion hole. As a result, the concentration of stress occurs at corners. As described above, in the case where an aluminum alloy is used as the material of the body in order to reduce the weight of the valve device, decline of the durability due to stress concentration becomes a problem. In order to suppress the stress concentration, it is conceivable to change a once-formed sharp angled corner or edge into an obtuse angle by a post-processing. However, the post-processing gives rise to a problem of un-ignorable increases in cost.